Lifting and positioning heavy objects during construction of a building often requires the combined efforts of a lift truck and one or more workers. The lift truck raises the object to the required height, and the workers shift the object on the forks of the lift truck so that the object is aligned or fits with other materials that are already in place. Construction in this manner can be a slow, difficult, and sometimes dangerous task, requiring several workers to maneuver the load into place if it is heavy and/or awkward to handle. This problem is not limited to the construction industry. For example, ware housing facilities are also faced with the problem of lifting and positioning building materials such as pipe, that must be stacked on shelving or in piles. Such materials must frequently be maneuvered into place after being raised, by repeated backing and turning the lift truck. Recognizing that the problem of lifting and maneuvering heavy objects exists in many industrial applications, others have attempted to develop devices that facilitate the handling of such loads.
For instance, apparatus for positioning structural members is disclosed in U.S. Pat. No. 3,409,158 (Lull). The patent describes a cage that is attached to the forks of a lift truck and contains hydraulic devices to rotate, pivot, and translate structural members into position. Lull's apparatus has several limitations, however, including its inability to translate members in more than one direction, its inability to lift objects except by means of the lift truck, and its inability to pivot an object relative to the base of the cage. In many circumstances, these limitations make precise positioning of materials difficult to accomplish, since the lift truck itself may need to be moved several times to achieve the desired positioning of an object, instead of simply positioning the lift truck in the general location and thereafter performing all precise positioning of the object solely by operator control of Lull's patented apparatus.
A materials handler is also disclosed in U.S. Pat. No. 3,087,630 (Karnow). This prior art materials handler is a relatively intricate and complicated omnidirectional manipulator that is unable to move and position materials over more than small incremental distances--at least not without repositioning the lift truck to which it is attached.
U.S. Pat. Nos. 4,392,524 (Bauch) and 4,666,365 (Cradeur) disclose lifts for handling heat exchanger bundles. The inventions disclosed in these two patents are not likely to be more useful than a simple forklift for lifting objects other than heat exchangers, since their ability to position an object is limited. For example, neither of these patents disclose means to tilt an object or means for pivoting the object.
In consideration of the limitations of the devices disclosed in the prior art discussed above, it should be apparent that an effective solution to the problem of positioning a load is not currently known. Accordingly, the present invention was developed, and it provides significant advantages over the prior art devices for handling materials that must be lifted and precisely positioned.